The crime novels of Ann Cleeves are helping tourism in "the last untamed
corner" of Britain. Liz Hunt joined the visitors.

It was still dark on the morning Detective Jimmy Perez was called to the Bird Observatory. The storm that had been raging around Fair Isle for days had yet to blow itself out.

Angela's body was slumped over her desk, the ivory handle of a knife protruding through the bloody silk of her blouse. In a macabre touch, her killer had threaded white feathers through her long, black hair, like a garland, and …

Sorry, but if you want to know who done it you'll have to read Blue Lightning, the fourth in the bestselling Shetland series of crime novels by Ann Cleeves, in which her hero, Jimmy Perez, investigates suspicious deaths that occur with regularity on this far-flung archipelago (population 22,000) off the north coast of Scotland.

Once it was big oil, small ponies, frenziedly patterned knitwear and the annual longboat burning ritual of Up Helly Aa that lured visitors; now it is the lugubrious Perez as fans seek out the real-life inspiration for the literary locations and characters.

Tourism chiefs are gleeful. As revenue from North Sea oil dries up, alternative sources of income are crucial. With Shetland recently voted the sixth ''best place in the world'' to visit in 2011 by the Lonely Planet Guide Best in Travel, and holidaying in Britain fashionably acceptable again, they are optimistic that this is a new era for ''the last untamed corner" of Britain.

Cleeves grew up in tamer climes, in Herefordshire and Devon. Her association with Shetland began in 1975 when she was 19, a university dropout who took a summer job as a cook at the Bird Observatory Lodge on Fair Isle, the most southerly of more than 100 islands that make up Shetland.

She stayed for two years and met her husband, Tim, who was working for the RSPB there. Since then, Shetland has been her passion: the stark beauty of the landscape, the isolation and rigour of the life, the savage storms and exquisite summer days, and the variety and uniqueness of its fauna and flora.

But it is the people, blessed with all the warmth and wariness of those born and bred in a small community, who draw her back year after year.

In the middle of the 19th century about 380 people lived on Fair Isle: today the figure is 70, a handful of young families but mostly the elderly or middle-aged, with crofting as their mainstay. And while the island can boast two historic Stevenson lighthouses, a chapel and a kirk – services are held at each on alternate Sundays – it has just one shop and no pub. During bad weather, which can last for weeks, the tiny airstrip is closed and the island ferry-cum-mail boat, Good Shepherd IV, confined to harbour.

It wasn't until 2003 that Cleeves began to write about Shetland. A novelist of almost 20 years' experience, she had met with limited success and recognition. That changed on the day a rare coot was spotted on Shetland mainland. Tim, a renowned ornithologist, and Ann, who is resolutely not a bird- watcher, flew up to Sumburgh airport from their then home in West Yorkshire to see it.

It was the dog end of the year and freezing cold at Clickimin Loch, just outside the capital, Lerwick. A huge orange sun was hanging low when Ann spotted three ravens on the shore. She was transfixed by the oily, black sheen of their plumage against the frozen snow.

''I thought: 'If there were blood as well, it would be like a fairy story. Snow White with her blood-red lips and all that.' I asked Tim if ravens would feed on a dead body and he said: 'Of course', and so I had the first scene.''

Raven Black was published in 2006 and won the Duncan Lawrie Dagger award for Best Crime Novel. Cleeves, a soft-spoken woman whose Bohemian style and gentle but determined manner hint at her early career as a probation officer, was whisked away on book tours to the United States and Japan, and found herself topping bestseller lists in Scandinavia and Germany.

At home, her publisher and fans were clamouring for a sequel. She obliged with White Nights, Red Bones and then Blue Lightning, all of which have been optioned for television. The last book is particularly close to her heart because it is set in the Bird Observatory where her love affair with Shetland began.

Her creation, Perez, is a Fair Isle man whose unlikely surname speaks of the ancestry she conjured for him. More than 100 ships have been wrecked off this tiny island, including, in 1588, a remnant of the storm-scattered Spanish Armada, El Gran Grifón (the wreck was discovered in 1970). Some survivors are said to have spent many weeks on the island: is it so unlikely that one or two stayed, perhaps falling for a local girl? Cleeves thought not.

Fair Isle, three miles long and 1.5 miles wide, lies equidistant between Shetland mainland and Orkney, and is the best known of the islands. In part this is because of the enduring marketability of its distinctive knitwear – said to be influenced by that brief Spanish invasion – which, for hundreds of years, the islanders used to barter with passing ships.

Back then it was gloves, hats, socks and underwear: the pullovers and cardigans came later, their popularity increasing after the then Prince of Wales took to sporting a Fair Isle V-neck through the Twenties.

In more recent times, the Observatory and Lodge have helped boost interest in, and the economy of, Britain's most remote inhabited island. Founded in 1948 by George Waterson, who owned Fair Isle (he sold it in 1954 to the National Trust for Scotland), its work revolves around the daily collection and analysis of data on seabirds and migratory birds and it attracts bird-watchers from throughout the world.

Located at the intersection of key flight paths from Scandinavia, Iceland and Faroe, the island provides a welcome temporary haven for migratory birds. The influx begins in late March and peaks in May; early June is the best time to spot the rarities that have the twitchers twitching frantically.

During the summer, it is the pungent smell and incessant cries of seabirds – gannet, shag, Arctic skua, great skua, kittiwake, Arctic tern and puffins – nesting on the northern cliffs and hills – that dominate. In late July, the autumn migration begins with waders returning from the Arctic and the Observatory fills with birdwatchers desperate to bag the famous Fair Isle ''specials'': lanceolated warbler, Pallas's grasshopper warbler, great snipe, the yellow-breasted bunting and the Pechora pipit.

Which is all very well if pipits and buntings are your thing, but what if they're not? Does Fair Isle offer anything for non-twitchers like me? Ann is adamant that it does.

''You don't have to be a birder to appreciate the beauty of Fair Isle – especially in the spring and summer when there are flowers everywhere and it's light nearly all night.

"I think it's a great place for families with kids because they're welcome at all the island events like dances and barbecues. And even if they're not birders when they arrive, there's something magic about seeing a bird close to when it is ringed.''

The Fair Isle adventure – there is no other way to describe it – begins with a short flight in a seven-seater plane, which is simultaneously exhilarating and terrifying if it's a gusty day, from Tingwall airport on Shetland mainland. The alternative option is a trip of more than two hours – even in good weather it's a challenge – from Grutness on the Good Shepherd IV, which sails three times a week during the summer.

And then, well, it is up to you, with a whole island to explore from tiny coves and inlets via peaty hills scattered with sheep to the rearing cliffs of Malcolm's Head. There are numerous walks to suit every ability, several sites of archaeological interest dating back to the Iron Age, and the remnants of a German plane from the Second World War.

Seals, whales, porpoises and dolphins are a feature of the summer months, while a small museum and arts-and-crafts workshops cater for visitors curious about island culture. For those who cannot fall asleep without the lullaby of the shipping forecast – ''Malin, Hebrides, Bailey, Fair Isle…'' – then the weather station, run by a crofter, Dave Wheeler (the former keeper at the South Light and the fire chief, who is also airstrip manager and radio operator), provides an insight into how it is compiled.

And, as I found to my surprise, it is difficult not to get caught up in the daily duties of the Observatory staff, from the early-morning trap rounds, to see which birds have arrived overnight, to the ritual of the evening log, where, over a drink in the bar, staff and visitors run through what they have seen and where – to be recorded by the warden.

The Lodge is working hard to attract more visitors outside peak migratory periods. Last year, a new eco-friendly building, with en-suite bedrooms and family rooms, a laundry and drying room, Wi-Fi and library, was opened, overlooking the tiny beach at the North Harbour. With full board starting at £50 per person per night, children under 12 at £20 and under-fives free, it makes for an economical family break that offsets the cost of travel.

My visit was enhanced by idyllic weather and I returned with an understanding of Cleeves' passion for Shetland and respect for those who live there. They are rare birds indeed. For the rest of us, the islands offer a quirky adventure holiday in one of Britain's last genuinely wild environments.